(#8010) Add getvar() rvalue function

This isn't directly related to #8010, but rather indirectly fills the
need to allow the end user to configure where data values are looked up.

This allows the namespace to be passed as a class parameter.  A module
may then quickly and easily look up data from the user-defined
namespace.

lib/puppet/parser/functions/getvar.rb

@@ -0,0 +1,23 @@
+module Puppet::Parser::Functions
+
+  newfunction(:getvar, :type => :rvalue, :doc => <<-'ENDHEREDOC') do |args|
+    Lookup a variable in a remote namespace.
+
+    For example:
+
+      $foo = getvar('site::data::foo')
+
+    This is useful if the namespace itself is stored in a string:
+
+      $bar = getvar("${datalocation}::bar")
+    ENDHEREDOC
+
+    unless args.length == 1
+      raise Puppet::ParseError, ("getvar(): wrong number of arguments (#{args.length}; must be 1)")
+    end
+
+    self.lookupvar("#{args[0]}")
+
+  end
+
+end

spec/unit/puppet/parser/functions/getvar_spec.rb

@@ -0,0 +1,53 @@
+require 'puppet'
+
+# We don't need this for the basic tests we're doing
+# require 'spec_helper'
+
+# Dan mentioned that Nick recommended the function method call
+# to return the string value for the test description.
+# this will not even try the test if the function cannot be
+# loaded.
+describe Puppet::Parser::Functions.function(:getvar) do
+
+  # Pulled from Dan's create_resources function
+  def get_scope
+    @topscope = Puppet::Parser::Scope.new
+    # This is necessary so we don't try to use the compiler to discover our parent.
+    @topscope.parent = nil
+    @scope = Puppet::Parser::Scope.new
+    @scope.compiler = Puppet::Parser::Compiler.new(Puppet::Node.new("floppy", :environment => 'production'))
+    @scope.parent = @topscope
+    @compiler = @scope.compiler
+  end
+
+  describe 'when calling getvar from puppet' do
+
+    it "should not compile when no arguments are passed" do
+      Puppet[:code] = 'getvar()'
+      get_scope
+      expect { @scope.compiler.compile }.should raise_error(Puppet::ParseError, /wrong number of arguments/)
+    end
+    it "should not compile when too many arguments are passed" do
+      Puppet[:code] = 'getvar("foo::bar", "baz")'
+      get_scope
+      expect { @scope.compiler.compile }.should raise_error(Puppet::ParseError, /wrong number of arguments/)
+    end
+
+    it "should lookup variables in other namespaces" do
+      pending "Puppet doesn't appear to think getvar is an rvalue function... BUG?"
+      Puppet[:code] = <<-'ENDofPUPPETcode'
+        class site::data { $foo = 'baz' }
+        include site::data
+        $foo = getvar("site::data::foo")
+        if $foo != 'baz' {
+          fail('getvar did not return what we expect')
+        }
+      ENDofPUPPETcode
+      get_scope
+      @scope.compiler.compile
+    end
+
+  end
+
+end
+